1. Field of the Invention
The present invention relates to a wireless input apparatus for use in information processing equipments such as personal computers, word processors and home game apparatuses.
2. Description of the Related Art
A conventional wireless input apparatus of this type is an input apparatus which transmits a signal to information processing equipments such as personal computers, word processors and home game apparatuses. For example, as shown in FIG. 9, a wireless input apparatus 101 is a keyboard having a light emitting diode 102. Each time any one of keys 105 of the keyboard is pressed, the wireless input apparatus 101 causes the light emitting diode 102 to emit light, thereby transmitting an optical signal corresponding to the pressed key. An information processing equipment 103 receives the optical signal transmitted from the light emitting diode 102 at a light receiving element 104, and determines which key of the keyboard was pressed based on an electric output of the light receiving element 104.
FIG. 10 is a block diagram schematically showing a structure of the wireless input apparatus 101. In FIG. 10, a switch matrix 111 is structured such that a plurality of scanning lines 112 and a plurality of receiving lines 113 intersect each other with a key switch 114 interposed between scanning line 112 and receiving line 113 at each of the intersections of the scanning lines 112 and the receiving lines 113. The key switches 114 at the intersections correspond to the respective keys in the keyboard. Accordingly, when any one of the keys is pressed, a key switch 114 corresponding to the pressed key is turned on, and a corresponding pair of scanning line 112 and receiving line 113 are electrically connected to each other through the key switch 114.
A microcomputer 115 sequentially scans the scanning lines 112. Accordingly, when any one of the key switches 114 is turned on and a corresponding pair of scanning line 112 and receiving line 113 are electrically connected to each other through the key switch 114, the microcomputer 115 identifies the key switch 114 based on a potential at the receiving line 113.
The microcomputer 115 applies an identification signal indicating the turning-on of the identified key switch 114 to an infrared light emitting diode 116, which in turn converts the identification signal from an electric signal to an optical signal for transmission.
When the identified key switch 114 is turned off thereafter, the corresponding scanning line 112 and the corresponding receiving line 113 are electrically disconnected from each other. Therefore, the receiving line 113 is rendered at high impedance, and the potential at the receiving line 113 is changed. The microcomputer 115 detects the turning-off of the identified key switch 114 at the time of scanning the corresponding scanning line 112 which had been electrically connected to the corresponding receiving line 113. Then, the microcomputer 115 applies an identification signal indicating the turning-off of the identified key switch 114 to the infrared light emitting diode 116, which in turn converts the identification signal from an electric signal to an optical signal for transmission.
A battery is used as a power supply 117. A voltage of the power supply 117 is supplied to the microcomputer 115 and an oscillator 118.
In the wireless input apparatus 101, in the case where the switch matrix 111 has not been operated for a prescribed period of time, oscillation of the oscillator 118 is stopped, whereby the operation of the microcomputer 115 is stopped. Thus, power consumption is reduced and the life of the power supply 117 is lengthened.
When any of the key switches 114 in the switch matrix 111 is turned on after oscillation of the oscillator 118 is stopped, oscillation of the oscillator 118 is resumed, whereby the microcomputer 115 is caused to start operating again.
Such a function to temporarily stop the oscillation of the oscillator 118 so as to lengthen the life of the power supply 117 is referred to as a key wake-up function. In other words, according to the key wake-up function, when software which carries out required procedures is executed, and therefore the switch matrix 111 has not been operated for a prescribed period of time, oscillation of the oscillator 118 for causing the microcomputer 115 to operate is stopped. When any one of the key switches 114 in the switch matrix 111 is turned on after the oscillation of the oscillator 118 is stopped, a prescribed signal is generated. In response to the signal, the oscillator 118 starts oscillating again, whereby the operation of the microprocessor 115 is resumed.
In the above-mentioned conventional wireless input apparatus, when the switch matrix 111 has not been operated for a prescribed period of time, the microcomputer 115 is stopped by the key wake-up function. Therefore, power consumption is minimized. However, when a book 121, for example, is placed on the wireless input apparatus 101 as shown in FIG. 11A or when the wireless input apparatus 101 is leaned against, for example, a wall 122, as shown in FIG. 11B, the key switches 114 in the switch matrix 111 might be turned on by accident. When any one of the key switches 114 is turned on, the microcomputer 115 is caused to operate by the key wake-up function. Moreover, the infrared light emitting diode 116 emits light in response to the turning-on of the key switch 114. In such a case as shown in FIGS. 11A and 11B, this condition could last for a long time. As a result, the power supply 117 is wasted, whereby the life of the power supply 117 is reduced.